The present invention relates to a progressive safety device for an elevator, the elevator car and the counterweight being guided and movable on guide rails, the elevator car or the counterweight being arrestable on the guide rails by means of a braking unit with an actuating unit.
The European Patent EP 1 283 189 B1 shows a progressive safety device for an elevator car. Arranged movably on a supporting element at right angles to a guide rail that guides the elevator car is a base plate. Arranged on the base plate is at least one actuating lever and opposite this a brake shoe. When the progressive safety device is actuated, the free end of the actuating lever comes into contact with the guide rail and is moved by the component of the frictional force that arises parallel to the guide rail, into the engaged position in which the guide rail is jammed between the free end of the actuating lever and the brake shoe.
The actuating lever can be actuated by means of a slide that is rotatable about an axis and which is itself actuatable by means of a rope of a speed governor, the speed governor arresting the rope should overspeed of the elevator car occur.
Through the relative movement of the elevator car relative to the arrested rope, the slide is put into a rotating movement and actuates the actuating lever.
A disadvantage of the known device is that actuation of the progressive safety device takes place via the governor rope. Rope oscillations in the governor rope that is stretched over the entire hoistway height can cause noises in the elevator car and lead to false actuation of the progressive safety device. The speed governor is a mechanically complex fault-prone device that requires space in the hoistway headroom and in the hoistway pit. Moreover, only one speed can be monitored.
Publication WO 00/39016 shows a progressive safety device for an elevator car. Provided as an actuating device instead of the governor rope is an electromagnet. In the activated state, the electromagnet holds a first latching lever fest, which itself holds a second latching lever at one end. The other end of the second latching lever engages in a groove of a spring-loaded pin that acts on an actuating lever. Arranged on the free end of the actuating lever is a locking roller which on actuation is moveable along a side of a wedge and which is wedged with the free web of the guide rail. When the electromagnet is switched into the current-free state, the first latching lever releases the second latching lever and the second latching lever releases the pin which by means of the spring force actuates the actuating lever.
A disadvantage of this known device is that, on actuation, the spring has to accelerate the pin and the actuating lever with the blocking roller arranged on the long lever of the actuating lever. This results in long dead times until the effective braking of the elevator car. Should the power supply fail, the power supply to the electromagnets must be buffered by means of an uninterruptible power supply so that no false actuations occur. Moreover, the safety device acts in only one direction and is only suitable for actuation at low speeds.